package com.mhtvs;

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

    public class SimpleCrypto {
    	/**
    	 * Usage:
    	 * <pre>
    	 * String crypto = SimpleCrypto.encrypt(masterpassword, cleartext)
    	 * ...
    	 * String cleartext = SimpleCrypto.decrypt(masterpassword, crypto)
    	 * </pre>
    	 * @author ferenc.hechler
    	 */
    	
        //String masterpassword = "somepassword";
        //String cleartext = "somecleartexthere";
        //String crypto = SimpleCrypto.encrypt(masterpassword, cleartext);
        //mytexttoset.setText(crypto)
    	
    	public static String encrypt(String seed, String cleartext) throws Exception {
    		byte[] rawKey = getRawKey(seed.getBytes());
    		byte[] result = encrypt(rawKey, cleartext.getBytes());
    		return toHex(result);
    	}
    	
    	public static String decrypt(String seed, String encrypted) throws Exception {
    		byte[] rawKey = getRawKey(seed.getBytes());
    		byte[] enc = toByte(encrypted);
    		byte[] result = decrypt(rawKey, enc);
    		return new String(result);
    	}

    	private static byte[] getRawKey(byte[] seed) throws Exception {
    		KeyGenerator kgen = KeyGenerator.getInstance("AES");
    		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
    		sr.setSeed(seed);
    	    kgen.init(128, sr); // 192 and 256 bits may not be available
    	    SecretKey skey = kgen.generateKey();
    	    byte[] raw = skey.getEncoded();
    	    return raw;
    	}

    	
    	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
    	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    		Cipher cipher = Cipher.getInstance("AES");
    	    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    	    byte[] encrypted = cipher.doFinal(clear);
    		return encrypted;
    	}

    	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
    	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    		Cipher cipher = Cipher.getInstance("AES");
    	    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
    	    byte[] decrypted = cipher.doFinal(encrypted);
    		return decrypted;
    	}

    	public static String toHex(String txt) {
    		return toHex(txt.getBytes());
    	}
    	public static String fromHex(String hex) {
    		return new String(toByte(hex));
    	}
    	
    	public static byte[] toByte(String hexString) {
    		int len = hexString.length()/2;
    		byte[] result = new byte[len];
    		for (int i = 0; i < len; i++)
    			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
    		return result;
    	}

    	public static String toHex(byte[] buf) {
    		if (buf == null)
    			return "";
    		StringBuffer result = new StringBuffer(2*buf.length);
    		for (int i = 0; i < buf.length; i++) {
    			appendHex(result, buf[i]);
    		}
    		return result.toString();
    	}
    	private final static String HEX = "0123456789ABCDEF";
    	private static void appendHex(StringBuffer sb, byte b) {
    		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
    	}
    	
    }
